The present invention relates to a filter and valve system and more particularly to such a system especially suited to aquarium pollution control.
Among the many problems associated with the keeping of tropical fish, filtration is by far the most important. The purpose of filtration is to reduce the level of pollution in the water while maintaining therein certain beneficial chemical and biological properties. Without some form of filtration, the chance of success in an aquarium is very slight.
Before considering the different types of filtration and their effect on pollution, it will be helpful to first consider the basic principles of pollution control. There are three basic requirements for controlling pollution: the aquarium must be kept (1) physically clean, (2) biologically clean and active, and (3) chemically clean and balanced.
Physically Clean
Water which is physically clean has no suspended particles. Many fish will not thrive in water that is not physically clean. In addition, an esthetically pleasing tank appearance is only possible with water that is physically clean. The gravel must also be kept somewhat free of debris or the flow of water through the gravel will be restricted. In a marine (salt-water) tank, this would have the effect of lowering the pH and decreasing the effectiveness of the bacteria. In this sense, the cleanliness of gravel directly affects the chemical and biological properties of the water. Gravel type filters are shown, for example, in U.S. Pat. No. 3,835,813 to Katz; U.S. Pat. No. 3,814,254 to Schatz; and numerous other references, in one form or another.
Biologically Clean and Active
Water which is biologically clean is relatively free of harmful organisms and harmful bacteria. It should also be free of superfluous suspended bacteria which would give the water a cloudy appearance. For an aquarium system to be biologically active, a growth of aerobic bacteria and nitrifying bacteria must be present and provided with some form of gravel bed. A large surface area on the filtering media would provide a large population of aerobic bacteria to decompose food and solid waste particles. The gravel bed supports the nitrifying bacteria which ultimately produce nontoxic nitrates from ammonia, carbon dioxide, oxygen, carbonate and bicarbonate. Where there is an inadequate flow of oxygenated water, decomposition can occur via the action of anaerobic bacteria to produce hydrogen sulfide and methane which are very toxic. A biological filtering system is described, for example, in U.S. Pat. No. 3,387,587 to Kelley et al and U.S. Pat. No. 3,835,813 to Katz (algae).
Chemically Clean and Balanced
Water which maintains the same chemical composition as when the tank was first set up would be chemically clean. However, tank inhabitants alter the chemical composition quickly using trace elements and adding organic compounds. Although activated carbon is somewhat experimental, it is very effective in removing a variety of substances when used carefully. Ion exchange resins have also been used to remove ammonia and nitrates but they are not usually necessary when a biological filter is working properly. It should be noted that the easiest method of keeping the water chemically clean is to make frequent partial water changes.
With these principles in mind we can look at filtration as it now works in aquarium systems. The three basic types of filters are (1) power filters, (2) undergravel filters, and (3) microfilters.
Power Filters
This type of filter is the most commonly used filter in both fresh and marine aquariums. A power filter usually consists of some sort of plastic container with a false bottom to hold the filter media, a siphon tube, and a motor connected to a rotor. The water from the aquarium is siphoned into the plastic container where it is passed through a filter media (usually polyester floss and carbon). The water then passes through the false bottom of the container to the motor driven rotor which serves to pump the cleaned water back into the tank. The advantage of using this type of filter is that it is fairly effective in removing particles from the water at a reasonable price. The disadvantages of this type of filter are many:
(1) They take up space in the back of an aquarium, with the larger and more effective filters taking up a great deal of space.
(2) By the nature of their design, the surface area of the filter media is limited in spite of the fact that most filtering is done on the surface of the filter media.
(3) The filtering relies on gravity which restricts the flow of water when the filter media becomes clogged. However, when the filter media becomes clogged, it filters smaller particles which makes it more effective. Therefore, a compromise must be made between maximum filter effectiveness and maximum water flow.
(4) Siphons are hard to start and may stop working if the water level drops a couple of inches.
(5) They are often noisy.
Undergravel Filters
Another type of filter which is used a great deal is the undergravel filter. This is used primarily for marine aquariums but is also effective in fresh water aquariums. This type of filter usually uses an air pump to create a water flow in tubes which run from the filter plate to the surface of the water. In this way, water is drawn through gravel and below the undergravel filter plate where it is lifted to the surface and the cycle is started again. The important role it plays in a marine aquarium is to buffer the pH of the water by using limestone or dolomite in place of gravel and having the water pass through this buffering process. The undergravel filter also allows water to pass through a bed of bacteria which maintains the biological filter. The advantages of this type of filter are its effectiveness and its reasonable cost. The disadvantages are as follows:
(1) Air pumps are often very noisy.
(2) The tubes needed for water lift clutter the aquarium.
(3) The tubes become clogged with debris and must be cleaned by removing the filter and gravel about once a year.
Microfilters
The category of microfilters is extremely limited at this time, but shows great promise. The most widely used microfilter is the "Diatom Filter" which uses diatomaceous earth powder as a filter media. This type of filter extracts microscopic particles under 20 microns. Various plastic cartridge microfilters are now made but not used in aquarium filters at the present time. The main disadvantage of the "Diatom Filter" is that it is complicated to use and very bulky. A properly designed microfilter would be of tremendous value in keeping tropical fish by creating sparkling clean water and removing most parasites and disease.
It is therefore a main object of this invention to provide a filtering system which combines the advantages of gravel filtration, particulate filtration, and microfiltration while overcoming the disadvantages previously encountered in these systems.
It is a related object to provide an effective filtering system for an aquarium which does not take up space behind the aquarium and may be formed as a single unit.
It is a further related object to provide a quiet and otherwise esthetically non-obtrusive filter for use in an aquarium.
It is a still further object to provide a filter valving and chamber system that provides for convenient back-washing or unclogging of the filter without removal from the aquarium.